Backlash take-up



Jan 3 1950 D. F. LJNSLEY 2,493@

BACKLASH TAKE-UP Filed April 27, 1945 74 76 6a, 79 C13/tmp i Patented Jan. 3, `1950 UNITED STATES PATENT OFFICE BACKLASH TAKE-UP Douglas F. Linsley, Greenwich, Conn. Application April 27, 1945, Serial No. 590,569

4 Claims. (Cl. 'i4-441) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) a means of substantially eliminating backlash.A

A further purpose of the invention is to provide a means of automatic backlash elimination.

Other purposes and advantages of the invention will become apparent from the preferred embodiment of the invention described hereinafter and illustrated in the accompanying drawings in which:

Figure 1 is a plan view of the lower half of the housing as taken along line I--I of Figure 2, and showing one form of the invention,

Figure 2 is a sectional view taken along the line 2-2 of Figure 1,

Figure 3 is a sectional transverse view of a modied form of the invention,

Figure 4 is a sectional view taken along line 4--4 of Figure 3, and

Figure 5 is a fragmentary enlarged sectional view taken along line 5--5 of Figure 1, but showing the axis of spring 56 and screw 2 in one plane and an increased number of screw threads engaged by the housing, for clarity of illustration only. f

Similar vreference characters indicate similar parts in all views.

This invention has particular utility in eliminating backlash between screw threads on a screw and those on a member in which it is threaded. The invention is more particularly concerned with the problem as it isencountered in precision instruments or like situations where the work done by or on the screw is relatively light but where the establishment and maintenance of a close working fit between the screw and its cooperating parts is of considerable importance 'to the accurate use ofl the instrument.

While devices and methods of taking up backlash are known in the art, the present invention shows a method of taking up backlash automatically and continuously if desired. A result is to lessen the need for some of the close tolerances normally required duringj manufacture.

Inaccordance with the invention, a screw 2 having threads 4 is rotatably mounted in a housing 6. The housing 6 has two abutting portions, as seen in Figure 2, the portions being, for convenience of description only, designated as the upper portion 8 and the lower portion I0. The lower portion I0 has a channel or recess I5 formed in itsy upper surface I4, and the upper heads 40 of screws 32.

portion 8 has an extension I8 extending downwardly into and lling the channel I6. It is preferable for some clearance to exist at I9 between the lower surface of extension I8 and the base of channel I6. As further observed in Figure 2, the lower surface I2 of the upper portion 8 is in sliding contact with the upper surface I4 of lower portion I0 at all points of contact between the two portions except at location I9.

A half-round recess 20 is formed in the upper surface of lower portion I0 and a corresponding half-round recess 22 is formed in the lower surface of upper portion 8, the two recesses matching and combining to form a bore 26 having internal threads and large enough to threadably receive screw 2. yThe portion of the internal threads in upper recess 22 is located at 28 and the portion of the internal threads in lower recess 20 is located at 30..

Members 8 and I0 are held in contact by means of screws 32 which pass through holes 34 in member 8 and are threaded into recesses 36 in member I0. Washers 38 may be located under the The holes 34 are made somewhat larger in inside diameter than the diameter of the screws 32 in order to allow the members 8 and I0 to slide over each other in a direction parallel to the axis of screw 2, as will be further explained below.

Cylindrical recesses 4I and 42 having their axes parallel to the axis of screw 2, and their centers located on lines 44 and 46 respectively and to either side of recess I6, are each formed vwith one 'hemicylindrical portion 48 in the lower surface I2 of upper portion 8 and the other hernicylindrical portion in the upper surface I4 of lower portion I0.

As indicated in Figure 5,.the upper hemicylindrical portion 48 is displaced at its ends from alignment with the corresponding ends of lower hemicylindrical portion 50 by a distance from location 52 to location 54. A coil spring 56 is located in each recess 4I and 42 under compression against disks 58 at each end of springs 56. It is thus apparent that the spring 56 exerts continuous pressure against end 60 of lower recess 50 in the direction of arrow 62, and exerts pressure against end 64 of upper recess 48 inthe opposite direction as indicated by arrow 6 6.- Thus the pressure of springs 56 tends to decrease the distance between locations 52 and 54. The result as seen in Figure is to cause the threads 28 of upper recess 22 to be pressed against the threads 4 of screw 2 in the direction of arrow 88. And similarly the threads 30 of lower recess 20 are pressed against the threads 4 of screw 2 in the opposite direction as indicated by arrow 82.

Accordingly the pressure of springs 58 takes up any existing clearance between the threads of screw 2 and the matching threads of bore 26 and backlash is thus eliminated.

As the existence of backlash becomes apparent. it is only necessary to loosen screws 32, thus al- A lowing the backlash to be eliminated as described above. the oversize holes I4 allowing the slightf Figure 2, use may be made of bolts 68 having slotted cylindrical heads 69 and each extending through a bore 12 formed in member I0. The bores 12 each have an enlarged portion 14 and a reduced portion 18. The bolt heads 69 have a diameter smaller than that of bore 14, being slidably disposed therein. A cylindrical coil spring 18 is located in each enlarged bore 14, being in contact under compression with bolt head 89 at one end and at the other end with the base or inner end of enlarged portion 14 formed by reduced portion 18. The bore 18 is not so small in diameter as to impede free movement of bolt 88 through it. Each bolt 88 also extends through an oversize bore 18 formed through member 8 as indicated, and a castle nut 82 with cotter pin 84 is fastened to its protruding threaded end. The bore 18 is sufficiently oversize to permit unrestrained limited sliding movement of members 8 and I0 relative to each other parallel to the axis of screw 2 as already' explained above, to take up any existing backlash, the compressive force of springs 18 suilicing to keep the members 8 and l0 in easy 4sliding contact without any binding.

By the additional structure shown in Figures 3 and 4, it is apparent that the springs 18 exert continuous yielding force to keep the abutting faces of members 8 and I8 in contact, but yet are not so strong that they prevent the springs 58 from taking up backlashas already explained By this means backlash is continuously and automatically taken up.and thus eliminated.

While I have described the invention in specific terms, it is to be understood thatyarious changes may be made in the sizes, shapes, materials and arrangement without departing from the -spint and scope of the invention as claimed.

I claim:

1. A housing having a threaded bore, a screw threaded into said bore, said housing being formed in two parts which are in slidable contact along a plane containing the axis of said screw so that a portion of said threaded bore lies in the mating faces of each of said parts, there being located in said mating faces but on opposite sides of said screw, a pair of cylindrical recesses, each recess thus being longitudinally split along said plane into two hemicylindrical recesses with their adjacent end Walls out of alignment, springs l0- cated in said cylindrical recesses and exerting a thrust urging said two parts into axial movement in respectively opposite directions to thereby take up any backlash existing between the threads on said bore and the mating threads on said screw.

2. A nut having a. threaded bore for engaging a screw and being split into an upper and a lower half along a plane parallel to and passing through the axis of said screw, spring means urging said two halves in opposite directions parallel to said axis, whereby the threads of said halves are pressed against the threads of Said screw in opposite directions, and spring means yieldingly urging said halves into engagement.

3. In a backlash take up nut for a. screw having a central longitudinal axis, first and second halves, said halves having complementary semi-cylindrical threaded channels cooperating to form a threaded hole for said nut, the confronting faces of said halves lying in a plane containing said axis, means holding said faces in engagement while permitting limited relative movement of the halves in a direction parallel with said axis, and

spring means acting between said halves and continuously urging them into such relative movement.

4. The construction of claim 3, said means holding said faces in engagement comprising a plurality of bolts each extending through oversize axially aligned bores in said halves, and coil springs on each said bolt and acting between the heads thereof and one said half to thereby yieldingly urge said halves into contact.

DOUGLAS F. LINSLEY.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 692,177 Burger J 1,647,480 starkey 2' 1,721,668 Parsons Juiy'za 1929 1,755,945 Alexandrescu Apr 22 1930 2,092,888 Maccoul sept. 14' 1937 2,192,188 Green Mar. 5' 1940 2,206,831 Bertheisen Ju1y 2' 1940 2,310,232 Haie Feb. 9', 1948 

